Retronasal sensory characterization of aroma compounds in Baijiu by detection threshold measurement, retronasal OAVs, and time-intensity evaluation.

The retronasal aroma of Baijiu is closely related to its quality and consumer preference. Retronasal detection thresholds (RDTs) of 44 aroma compounds were determined in 46% v/v ethanol using a three-alternative forced-choice procedure, which varied widely and ranged from less than 0.02 to over 1,000,000 µg/L. Nineteen aroma compounds, including ß-phenylethanol, 2,3,5,6-tetramethylpyrazine, dimethyl trisulfide, and 2-methyl-3-(methyldisulfanyl)furan, had RDTs lower than their orthonasal detection thresholds. Power function curves were used to establish correlations between RDTs and partition coefficients for five esters and four pyrazines (R2  = 0.9575, 0.9969, respectively). Twenty-nine aroma compounds had retronasal odor activity values >1 in a soy sauce aroma type Baijiu. Additionally, time-intensity (TI) results suggested that hexanoic acid, ethyl hexanoate, isoamyl acetate, 3-methyl-butanal, and nonanal contributed to a "burst-aroma" of Baijiu. Conversely, TI results attributed the "after-odor" of Baijiu to dimethyl trisulfide, methional, 2,3,5,6-tetramethylpyrazine, ß-phenylethanol, and other compounds. PRACTICAL APPLICATION: This manuscript provides comprehensive information on the retronasal sensory characteristics of aroma compounds in Baijiu. The results obtained may help understand the contribution of aroma compounds to retronasal aroma perception during Baijiu tasting and give helpful information to the Baijiu industry regarding quality control.

The evolutionary mechanism and function analysis of two subgroups of histamine-producing and non-histamine-producing Tetragenococcus halophilus.

Tetragenococcus halophilus is a halophilic bacterium that existed in the fermentation of soy sauce and miso for flavor production and probiotic benefits. However, it is composed of two subgroups, histamine-producing and non-histamine-producing, with the former causing histamine accumulation and offering risks to food safety. Exploring the evolutionary mechanisms and physiological function of histamine-biosynthesis is of significance for understanding the formative mechanism of T. halophilus's strain-specificity and is helpful for microbial control. Using systematic genomic analysis, we found that plasmid acquisition and loss is the evolutionary form resulting in the two subgroups of T. halophilus. Two plasmids, plasmid α with 30 kb and plasmid ß with 4 kb existed in histamine-producing T. halophilus. We investigated the whole genetic information and proposed their genetic function in both two plasmids. The acquisition of histamine-producing plasmid enhanced the acid tolerance of histamine-producing T. halophilus but did not affect salt tolerance. More interestingly, we found that the existence of plasmid will promote the co-culture growth of T. halophilus. This study deepens our understanding of the formative mechanism of microbial species diversity, and provides our knowledge of the physiological function of histamine-producing plasmids.

Glycogen for lysosome-targeted CpG ODNs delivery and enhanced cancer immunotherapy.

CpG oligodeoxynucleotides (ODNs) strongly activate the immune system after binding to toll-like receptor 9 (TLR9) in lysosome, which demonstrated significant potential in cancer immunotherapy. However, their therapeutic efficacy is limited by drawbacks such as rapid degradation and poor cellular uptake. Although encouraging progress have been made on developing various delivery systems for CpG ODNs, safety risks of the synthetic nanocarriers as well as the deficient CpG ODNs release within lysosome remain big obstacles. Herein, we developed a novel nanovector for lysosome-targeted CpG ODNs delivery and enhanced cancer immunotherapy. Natural glycogen was simply aminated (NH2-Gly) through grafting with diethylenetriamine (DETA), which was spherical in shape with diameter of approximately 40 nm. NH2-Gly possessed good biocompatibility. Cationic NH2-Gly complexed CpG ODNs well and protected them from nuclease digestion. NH2-Gly significantly enhanced the cellular uptake of CpG ODNs. Efficient CpG ODNs release was observed in the presence of α-glucosidase that mimicking the environment of lysosome. Consequently, NH2-Gly/CpG complexes triggered potent antitumor immunity and effectively inhibit the tumor growth without causing any toxic effect or tissue damages. This work highlights the promise of glycogen for lysosome-targeted on-command delivery of CpG ODNs, which brings new hope for precision cancer immunotherapy.

Higher-order matrix nonlinear Schrödinger equation with the negative coherent coupling: binary Darboux transformation, vector solitons, breathers and rogue waves.

Optical fiber communication plays a crucial role in modern communication. In this work, we focus on the higher-order matrix nonlinear Schrödinger equation with negative coherent coupling in a birefringent fiber. For the slowly varying envelopes of two interacting optical modes, we construct a binary Darboux transformation using the corresponding Lax pair. With vanishing seed solutions and the binary Darboux transformation, we investigate vector degenerate soliton and exponential soliton solutions. By utilizing these soliton solutions, we demonstrate three types of degenerate solitons and double-hump bright solitons. Furthermore, considering non-vanishing seed solutions and applying the binary Darboux transformation, we obtain vector breather solutions, and present the vector single-hump beak-type Akhmediev breather, Kuznetsov-Ma breathers, double-hump beak-type Akhmediev breather, Kuznetsov-Ma breathers, and vector degenerate beak-type breathers. Additionally, we take the limit in the breather solutions and derive vector rogue wave solutions. We illustrate the beak-type rogue waves and bright-dark rogue waves. Humps of these vector double-hump waves can separate into two individual humps. The results obtained in this work may potentially provide valuable insights for experimentally manipulating the separation of two-hump solitons, breathers, and rogue waves in optical fibers.

Estimating the completeness of physician billing claims for diabetes case ascertainment: a multiprovince investigation. / Estimation de l'exhaustivité des demandes de remboursement des médecins dans une optique de détermination des cas de diabète : étude menée dans plusieurs provinces.

INTRODUCTION: Previous research has suggested that how physicians are paid may affect the completeness of billing claims for estimating chronic disease. The purpose of this study is to estimate the completeness of physician billings for diabetes case ascertainment. METHODS: We used administrative data from eight Canadian provinces covering the period 1 April 2014 to 31 March 2016. The patient cohort was stratified into two mutually exclusive groups based on their physician remuneration type: fee-for-service (FFS), for those paid only on that basis; and non-fee-for-service (NFFS). Using diabetes prescription drug data as our reference data source, we evaluated whether completeness of disease case ascertainment varied with payment type. Diabetes incidence rates were then adjusted for completeness of ascertainment. RESULTS: The cohort comprised 86 110 patients. Overall, equal proportions received their diabetes medications from FFS and NFFS physicians. Overall, physician payment method had little impact upon the percentage of missed diabetes cases (FFS, 14.8%; NFFS, 12.2%). However, the difference in missed cases between FFS and NFFS varied widely by province, ranging from -1.0% in Nova Scotia to 29.9% in Newfoundland and Labrador. The difference between the observed and adjusted disease incidence rates also varied by province, ranging from 22% in Prince Edward Island to 4% in Nova Scotia. CONCLUSION: The difference in the loss of cases by physician remuneration method varied across jurisdictions. This loss may contribute to an underestimation of disease incidence. The method we used could be applied to other chronic diseases for which drug therapy could serve as reference data source.

Entering an Era of Protein Structuromics.

Sequence determines the structure, and the structure in turn determines the function, are the fundamental principles of protein chemistry. In the genomics era, the paradigm of mining protein functionality and evolutionary insights through sequence analysis has led to remarkable achievements. However, protein sequences often mutate faster than their structural counterparts during evolution. For protein sets characterized by highly divergent sequences, sequence-based analysis is often inadequate, whereas direct extraction of implicit information from the structures appears to be a more effective strategy.

Serine Improves Lactic Acid Stress Tolerance and Ethanol Production in Zygosaccharomyces bailii in Baijiu Fermentation.

Lactic acid is the primary inhibitor of the growth and ethanol production of yeasts in Baijiu fermentation. Certain amino acids have been found to be related to stress tolerance in yeasts. This study explored the effect of lactic acid stress on the ethanol-producing yeast Zygosaccharomyces bailii and evaluated the ability of serine to increase the lactic acid tolerance of Z. bailii in vitro. Serine significantly improved Z. bailii viability by 16.5% and ethanol production by 226.6% under lactic acid stress. Under lactic acid stress, serine supplementation led to an increase of 41.9% in cell wall integrity, 31.9% in cell membrane integrity, 296.6% in intracellular adenosine triphosphate (ATP), and 18.4% in the mitochondrial membrane potential. Finally, field emission scanning electron microscopy (FESEM) indicated that serine supplementation maintained the cell shape and reduced cell leakage. This study revealed a novel lactic acid tolerance mechanism of core functional yeasts during Jiang-flavor Baijiu fermentation.

Regulating the stereoselectivity of medium-chain dehydrogenase/reductase by creating an additional active pocket accommodating prochiral heterocyclic ketones.

Medium chain dehydrogenase/reductase (MDR) is a robust catalyst for the asymmetric synthesis of chiral heterocyclic alcohols, essential building blocks in pharmaceuticals. However, the regulatory mechanism of stereoselective complementary reduction of heterocyclic ketones by carbonyl reductase (CR) is unclear. Structure-guided creation of an additional substrate-binding active pocket inversed the stereoselectivity of SpCR from Spathaspora passalidarum. The mutant m48 showed improved catalytic activity towards the 12 tested heterocyclic ketones (conversion rate >99%, ee value > 99%). Hence, we regulated the stereoselectivity of MDR by creating an active pocket suitable for substrate localisation. This strategy has a guiding significance in addition to the conventional method for stereoselectivity modification of MDR.

A path planning method using modified harris hawks optimization algorithm for mobile robots.

Path planning is a critical technology that could help mobile robots accomplish their tasks quickly. However, some path planning algorithms tend to fall into local optimum in complex environments. A path planning method using a modified Harris hawks optimization (MHHO) algorithm is proposed to address the problem and improve the path quality. The proposed method improves the performance of the algorithm through multiple strategies. A linear path strategy is employed in path planning, which could straighten the corner segments of the path, making the obtained path smooth and the path distance short. Then, to avoid getting into the local optimum, a local search update strategy is applied to the HHO algorithm. In addition, a nonlinear control strategy is also used to improve the convergence accuracy and convergence speed. The performance of the MHHO method was evaluated through multiple experiments in different environments. Experimental results show that the proposed algorithm is more efficient in path length and speed of convergence than the ant colony optimization (ACO) algorithm, improved sparrow search algorithm (ISSA), and HHO algorithms.

mTORC1 Signaling and Negative Lens-Induced Axial Elongation.

Purpose: The mechanism underlying axial elongation during myopia progression remains unknown. Epidermal growth factor receptor (EGFR) signaling is associated with axial elongation. We explored whether mammalian target of rapamycin complex 1 (mTORC1) signaling acts as the downstream pathway of EGFR and participates in negative lens-induced axial elongation (NLIAE). Methods: Three-week-old male pigmented guinea pigs underwent binocular NLIAE. (1) To investigate whether EGFR is the upstream regulator of mTORC1, an EGFR inhibitor (20 µg erlotinib) was intravitreally injected once a week for three weeks. (2) To assess the effect of mTORC1 inhibition on NLIAE, an mTORC1 inhibitor (2 µg, 10 µg, and 20 µg everolimus) was intravitreally injected once a week for three weeks. (3) To explore the long-term effect of mTORC1 overactivation on axial elongation, an mTORC1 agonist (4 µg MHY1485) was intravitreally injected once a week for three months. Biometric measurements included axial length and choroidal thickness were performed. Results: Compared with the guinea pigs without NLIAE, NLIAE was associated with activation of mTORC1 signaling, which was suppressed by intravitreal erlotinib injection. Intravitreally injected everolimus suppressed NLIAE-induced axial elongation, mTORC1 activation, choroidal thinning, and hypoxia-inducible factor-1α expression in the sclera. Immunofluorescence revealed that the retinal pigment epithelium was the primary location of mTORC1 activation during NLIAE. Combining NLIAE and MHY1485 intravitreal injections significantly promoted axial elongation, choroidal thinning, and peripapillary choroidal atrophy. Conclusions: The mTORC1 signaling is associated with increased axial elongation, as in NLIAE, raising the possibility of inhibiting mTORC1 as a novel treatment for slowing myopia progression.

Efficacy and Safety of Ciprofol Sedation in ICU Patients Undergoing Mechanical Ventilation: A Multicenter, Single-Blind, Randomized, Noninferiority Trial.

OBJECTIVES: To determine the effectiveness and safety of ciprofol for sedating patients in ICUs who required mechanical ventilation (MV). DESIGN: A multicenter, single-blind, randomized, noninferiority trial. SETTING: Twenty-one centers across China from December 2020 to June 2021. PATIENTS: A total of 135 ICU patients 18 to 80 years old with endotracheal intubation and undergoing MV, who were expected to require sedation for 6-24 hours. INTERVENTIONS: One hundred thirty-five ICU patients were randomly allocated into ciprofol ( n = 90) and propofol ( n = 45) groups in a 2:1 ratio. Ciprofol or propofol were IV infused at loading doses of 0.1 mg/kg or 0.5 mg/kg, respectively, over 4 minutes ± 30 seconds depending on the physical condition of each patient. Ciprofol or propofol were then immediately administered at an initial maintenance dose of 0.3 mg/kg/hr or 1.5 mg/kg/hr, to achieve the target sedation range of Richmond Agitation-Sedation Scale (+1 to -2). Besides, continuous IV remifentanil analgesia was administered (loading dose: 0.5-1 µg/kg, maintenance dose: 0.02-0.15 µg/kg/min). MEASUREMENTS AND MAIN RESULTS: Of the 135 patients enrolled, 129 completed the study. The primary endpoint-sedation success rates of ciprofol and propofol groups were 97.7% versus 97.8% in the full analysis set (FAS) and were both 100% in per-protocol set (PPS). The noninferiority margin was set as 8% and confirmed with a lower limit of two-sided 95% CI for the inter-group difference of -5.98% and -4.32% in the FAS and PPS groups. Patients who received ciprofol had a longer recovery time ( p = 0.003), but there were no differences in the remaining secondary endpoints (all p > 0.05). The occurrence rates of treatment-emergent adverse events (TEAEs) or drug-related TEAEs were not significantly different between the groups (all p > 0.05). CONCLUSIONS: Ciprofol was well tolerated, with a noninferior sedation profile to propofol in Chinese ICU patients undergoing MV for a period of 6-24 hours.

CoNi Alloys Encapsulated in N-Doped Carbon Nanotubes for Stabilizing Oxygen Electrocatalysis in Zinc-Air Battery.

Alloy-based catalysts with high corrosion resistance and less self-aggregation are essential for oxygen reduction/evolution reactions (ORR/OER). Here, via an in situ growth strategy, NiCo alloy-inserted nitrogen-doped carbon nanotubes were assembled on a three-dimensional hollow nanosphere (NiCo@NCNTs/HN) using dicyandiamide. NiCo@NCNTs/HN exhibited better ORR activity (half-wave potential (E1/2) of 0.87 V) and stability (E1/2 shift of only -13 mV after 5000 cycles) than commercial Pt/C. NiCo@NCNTs/HN displayed a lower OER overpotential (330 mV) than RuO2 (390 mV). The NiCo@NCNTs/HN-assembled zinc-air battery exhibited high specific-capacity (847.01 mA h g-1) and cycling-stability (291 h). Synergies between NiCo alloys and NCNTs facilitated the charge transfer to promote 4e- ORR/OER kinetics. The carbon skeleton inhibited the corrosion of NiCo alloys from surface to subsurface, while inner cavities of CNTs confined particle growth and the aggregation of NiCo alloys to stabilize bifunctional activity. This provides a viable strategy for the design of alloy-based catalysts with confined grain-size and good structural/catalytic stabilities in oxygen electrocatalysis.

Semi-Rational Design of L-Isoleucine Dioxygenase Generated Its Activity for Aromatic Amino Acid Hydroxylation.

Fe (II)-and 2-ketoglutarate-dependent dioxygenases (Fe (II)/α-KG DOs) have been applied to catalyze hydroxylation of amino acids. However, the Fe (II)/α-KG DOs that have been developed and characterized are not sufficient. L-isoleucine dioxygenase (IDO) is an Fe (II)/α-KG DO that specifically catalyzes the formation of 4-hydroxyisoleucine (4-HIL) from L-isoleucine (L-Ile) and exhibits a substrate specificity toward L-aliphatic amino acids. To expand the substrate spectrum of IDO toward aromatic amino acids, in this study, we analyzed the regularity of the substrate spectrum of IDO using molecular dynamics (MD) simulation and found that the distance between Fe2+, C2 of α-KG and amino acid chain's C4 may be critical for regulating the substrate specificity of the enzyme. The mutation sites (Y143, S153 and R227) were also subjected to single point saturation mutations based on polarity pockets and residue free energy contributions. It was found that Y143D, Y143I and S153A mutants exhibited catalytic L-phenylalanine activity, while Y143I, S153A, S153Q and S153Y exhibited catalytic L-homophenylalanine activity. Consequently, this study extended the substrate spectrum of IDO with aromatic amino acids and enhanced its application property.

Electronic-State Modulation of Metallic Co-Assisted Co7 Fe3 Alloy Heterostructure for Highly Efficient and Stable Overall Water Splitting.

Manipulating electronic structure of alloy-based electrocatalysts can eagerly regulate its catalytic efficiency and corrosion resistance for water splitting and fundamentally understand the catalytic mechanisms for oxygen/hydrogen evolution reactions (OER/HER). Herein, the metallic Co-assisted Co7 Fe3 alloy heterojunction (Co7 Fe3 /Co) embeds in a 3D honeycomb-like graphitic carbon is purposely constructed as a bifunctional catalyst for overall water splitting. As-marked Co7 Fe3 /Co-600 displays the excellent catalytic activities in alkaline media with low overpotentials of 200 mV for OER and 68 mV for HER at 10 mA cm-2 . Theoretical calculations reveal the electronic redistribution after coupling Co with Co7 Fe3 , which likely forms the electron-rich state over interfaces and the electron-delocalized state at Co7 Fe3 alloy. This process changes the d-band center position of Co7 Fe3 /Co and optimizes the affinity of catalyst surface to intermediates, thus promoting the intrinsic OER/HER activities. For overall water splitting, the electrolyzer only requires a cell voltage of 1.50 V to achieve 10 mA cm-2 and dramatically retains 99.1% of original activity after 100 h of continuous operation. This work proposes an insight into modulation of electronic state in alloy/metal heterojunctions and explores a new path to construct more competitive electrocatalysts for overall water splitting.

Study Protocol of a Multicenter, Randomized, Single-Blind Trial: Efficacy and Safety of Remimazolam Tosylate for Sedation in ICU Patients.

INTRODUCTION: Pharmacodynamic and pharmacokinetic studies in animal experiments and a phase 1 study suggested remimazolam tosylate as an effective and safe sedation/anesthetic agent. However, the effects and safety dose of remimazolam for light sedation in intensive care unit (ICU) patients are not clear and should be confirmed in a phase 2 study. METHODS: Sixty ICU patients requiring sedation treatment and undergoing mechanical ventilation will be enrolled and randomly assigned to a high dose group (HD group, 30 cases) and a low dose group (LD group, 30 cases) in a 1:1 ratio. Patients in both groups will be sedated using remimazolam tosylate in a primary dose of 0.08 mg/kg and a range of 0-2.0 mg/kg/h after randomization. Dose adjustment will be made at the range of every 0.1 mg/kg/h in the LD group and 0.2 mg/kg/h in the HD group to maintain the target Richmond Agitation and Sedation Score (RASS) at - 2 to + 1. The primary outcome will be the proportion of subjects that meet the following conditions: the time within the range of RASS (- 2 to + 1) accounts for 70% of the study drug administration time; without other rescue treatments. Secondary outcomes including the percentage time to reach the sedation goal; the proportion of subjects receiving rescue sedation and/or analgesic, and the mean dose of rescue drug throughout the study period; duration of mechanical ventilation; recovery time to full consciousness and nursing scores. Evaluations of safety including adverse events (AEs), serious AEs, physical examination, laboratory examination, etc. OUTCOME: The results of this study will provide crucial information for the use of remimazolam tosylate for ICU sedation. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT05152303.

Amino Acids Drive the Deterministic Assembly Process of Fungal Community and Affect the Flavor Metabolites in Baijiu Fermentation.

Nutrient fluctuation is ubiquitous in fermentation ecosystems. However, the microbial community assembly mechanism and metabolic characteristics in response to nutrient variation are still unclear. Here, we used Baijiu fermentation as a case example to study the responses of microbial community assembly and metabolic characteristics to the variation of amino acids using high-throughput sequencing and metatranscriptomics analyses. We chose two fermentation groups (group A with low amino acid and group B with high amino acid contents). The two groups showed similar succession patterns in the bacterial community, whereas they showed different succession in the fungal community wherein Pichia was dominant in group A and Zygosaccharomyces was dominant in group B. The ß-nearest taxon index (ßNTI) revealed that bacterial community was randomly formed, whereas fungal community assembly was a deterministic process. Variance partitioning analysis and redundancy analysis revealed that amino acids showed the largest contribution to the fungal community (37.64%, P = 0.005) and were more tightly associated with it in group B. Further study revealed that serine was positively related to Zygosaccharomyces and promoted its growth and ethanol production. Metatranscriptomic analysis revealed that the differential metabolic pathways between the two groups mainly included carbohydrate metabolism and amino acid metabolism, which explained the differences of ethanol production and volatile metabolites (such as isoamylol, isobutanol, and 2-methyl-1-butanol). Then these metabolic pathways were constructed and related gene expression and active microorganisms were listed. Our study provides a systematical understanding of the roles of amino acids in both ecological maintenance and flavor metabolism in fermentation ecosystems. IMPORTANCE In spontaneous fermented foods production, nutrient fluctuation is a critical factor affecting microbial community assembly and metabolic function. Revealing the microbial community assembly mechanism and how it regulates its metabolic characteristics in response to nutrient variation is helpful to the management of the fermentation process. This study provides a systematical understanding of the effect of amino acids on the microbial community assembly and flavor metabolisms using Baijiu fermentation as a case example. The data of this study highlight the importance of the nutrient management in fermentation ecosystems.

Aspirin Therapy and 28-Day Mortality in ICU Patients: A Retrospective Observational Study From Two Large Databases.

PURPOSE: Aspirin is widely used in patients in the intensive care unit (ICU); nonetheless, its effects on these patients remain controversial. This retrospective analysis of data from clinical practice investigated the effects of aspirin on 28-day mortality in ICU patients. METHODS: This retrospective study included data from patients in the Medical Information Mart for Intensive Care (MIMIC)-III database and the eICU-Collaborative Research Database (CRD). Patients aged 18 to 90 years and admitted to the ICU were eligible and were assigned to one of two groups according to whether they were given aspirin during their ICU stay. Multiple imputation was used for patients with >10% missing data. Multivariate Cox models and propensity score analysis were used to estimate the association of aspirin treatment with 28-day mortality among patients admitted to the ICU. FINDINGS: In total, 146,191 patients were enrolled in this study, and 27,424 (18.8%) used aspirin. Aspirin treatment in ICU patients, especially in nonseptic patients, was associated with a lower 28-day all-cause mortality on multivariate Cox analysis (eICU-CRD, hazard ratio [HR] = 0.81, [95% CI, 0.75-0.87]; MIMIC-III, HR = 0.72 [95% CI, 0.68-0.76]). Aspirin treatment was associated with lower 28-day all-cause mortality after propensity score matching (eICU-CRD, HR = 0.80 [95% CI, 0.72-0.88]; MIMIC-III, HR = 0.80 [95% CI, 0.76-0.85]). However, on subgroup analysis, aspirin therapy was not associated with a lower 28-day mortality in patients without systemic inflammatory response syndrome (SIRS) symptoms or with sepsis in either database. IMPLICATIONS: Aspirin treatment during the ICU stay was associated with a significantly reduced 28-day all-cause mortality, particularly in patients with SIRS symptoms but without sepsis. In patients with sepsis and with/without SIRS symptoms, beneficial effects were not clear, or more careful patient selection is required.

Ratio of Histamine-Producing/Non-Histamine-Producing Subgroups of Tetragenococcus halophilus Determines the Histamine Accumulation during Spontaneous Fermentation of Soy Sauce.

Strain specificity (within-species variation) of microorganisms occurs widely in nature. It might affect microbiome construction and function in a complex microbial environment. Tetragenococcus halophilus, a halophilic bacterium that generally is used in high salt food fermentation, consists of two histamine-producing and non-histamine-producing subgroups. It is unclear whether and how the strain specificity of histamine-producing capacity influences the microbial community function during food fermentation. Here, based on systematic bioinformatic analysis, histamine production dynamic analysis, clone library construction analysis, and cultivation-based identification, we identified that T. halophilus is the focal histamine-producing microorganism during soy sauce fermentation. Furthermore, we discovered that a larger number and ratio of histamine-producing subgroups of T. halophilus significantly contributed more histamine production. We were able to artificially decrease the ratio of histamine-producing to non-histamine-producing subgroups of T. halophilus in complex soy sauce microbiota and realized the reduction of histamine by 34%. This study emphasizes the significance of strain specificity in regulating microbiome function. This study investigated how strain specificity influenced microbial community function and developed an efficient technique for histamine control. IMPORTANCE Inhibiting the production of microbiological hazards under the assumption of stable and high-quality fermentation is a critical and time-consuming task for the food fermentation industry. For spontaneously fermented food, it can be realized theoretically by finding and controlling the focal hazard-producing microorganism in complex microbiota. This work used histamine control in soy sauce as a model and developed a system-level approach to identify and regulate the focal hazard-producing microorganism. We discovered that the strain specificity of focal hazard-producing microorganisms had an important impact on hazard accumulation. Microorganisms frequently exhibit strain specificity. Strain specificity is receiving increasing interest since it determines not only microbial robustness but also microbial community assembly and microbiome function. This study creatively explored how the strain specificity of microorganisms influenced microbiome function. In addition, we believe that this work provides an excellent model for microbiological hazard control which can promote future work in other systems.

R97 at "Handlebar" Binding Mode in Active Pocket Plays an Important Role in Fe(II)/α-Ketoglutaric Acid-Dependent Dioxygenase cis-P3H-Mediated Selective Synthesis of (2S,3R)-3-Hydroxypipecolic Acid.

Pipecolic acid (Pip) and its derivative hydroxypipecolic acids, such as (2S,3R)-3-hydroxypipecolic acid (cis-3-L-HyPip), are components of many natural and synthetic bioactive molecules. Fe(II)/α-ketoglutaric acid (Fe(II)/2-OG)-dependent dioxygenases can catalyze the hydroxylation of pipecolic acid. However, the available enzymes with desired activity and selectivity are limited. Herein, we compare the possible candidates in the Fe(II)/2-OG-dependent dioxygenase family, and cis-P3H is selected for potentially catalyzing selective hydroxylation of L-Pip. cis-P3H was further engineered to increase its catalytic efficiency toward L-Pip. By analyzing the structural confirmation and residue composition in substrate-binding pocket, a "handlebar" mode of molecular interactions is proposed. Using molecular docking, virtual mutation analysis, and dynamic simulations, R97, E112, L57, and G282 were identified as the key residues for subsequent site-directed saturation mutagenesis of cis-P3H. Consequently, the variant R97M showed an increased catalytic efficiency toward L-Pip. In this study, the kcat/Km value of the positive mutant R97M was about 1.83-fold that of the wild type. The mutation R97M would break the salt bridge between R97 and L-Pip and weaken the positive-positive interaction between R97 and R95. Therefore, the force on the amino and carboxyl groups of L-Pip was lightly balanced, allowing the molecule to be stabilized in the active pocket. These results provide a potential way of improving cis-P3H catalytic activity through rational protein engineering.

The formation and structural characteristics of melanoidins from fermenting and distilled grains of Chinese liquor (baijiu).

Chinese liquor (baijiu) is a typical fermented food. In which production, melanoidins are formed in fermenting grains during low-temperature fermentation with long-term, and in distilled grains with high-temperature distillation for short-term. Here, the formation and structural characterization of melanoidins in these two distinct stages were first investigated through chemical composition analysis and spectroscopic identification. Our research showed that proteins and phenols continuously participate in melanoidin formation during fermentation and distillation processes. Distillation could produce melanoidins with larger amounts, darker colors, higher molecular weights, and more stable states than fermentation. The chemical composition including 10 carbohydrates, 17 amino acids, 5 free phenolic acids, and 7 bound phenolic acids was successfully identified in melanoidins. Ion chromatography was proposed to be an efficient method to investigate carbohydrates in melanoidins. Moreover, the potential impact of microorganisms on melanoidins was first revealed to be the possible utilization of glucose in melanoidins.